Process for producing clad metal plates by explosive bonding



April 16, 1968 TwosHl FuKuMoTo 3,377,693

PROCESS FOR PRODUCING CLAD METAL PLATES BY EXPLOSIVE BONDING April 16, l968 TlYosHl FUKuMoTo 3,377,693

` `PROCESS FOR PRODUCING CLAD METAL PLATES BY EXPLOSIVE BONDING Filedsept. 22, 1965 2 sheets-sheet e United States Patent O 3,377,693 PROCESSFR PREUCHNG CLAD lVlETAL PLATES BY EXPLOSIVE ENDING Tiyoshili'rrirumoto, (lita-shi, Japan, assigner' to Asahi Kaseio KogyoKahushilri Kaisha, Gsaka, `lapan, a corporation of .iapan Filed Sept.22, 1965, Ser. No. 489,336 Claims priority, application Japan, Sept. 24,1964i, FaQ/53,9%; May 26, 1965, #t/30,661 6 Claims. (Cl. 29-470.l)

ABSTRACT 0F THE DISCLOSURE A process for bonding the same or differentmetal plates by the detonation pressure of an explosive wherein an angleis formed between a cladding metal plate and a base metal plate of from0.1 to 0.5 in a lirst region, and a larger angle of between 0.3 to 1.2is formed between the plates in a second region. The cladding plate issuperimposed on the base plate so that said first region extends over 45to 80 percent of the base plate. An explosive is placed on a butterabove the cladding plate and detonation is effected at one end of therst region so that detonation proceeds from the first region to thesecond region.

The present invention relates to a process for producing clad plates,which comprises bonding a metal plate with a plate of the same ordiierent kind by detonation pressure of an explosive. The conventionalprocesses such as the rolling method, vapor deposition method, facebuild-up method, fusion welding method, etc. have many faults.

In contrast to this, there is merit in a recently developed process forpreparing a clad plate by the detonation pressure of an explosive, ascompared with the conventional processes. Therefore, it has beenextensively investigated in many places. This process involves preparingclad plates `under cold working by superimposing a metal plate (whichwill be called a cladding metal, hereinafter) and composed for exampleof corrosionresistant metal, with a certain spacing, upon a metal plate(which will be called a base metal, hereinafter) and composed forexample of low-priced mild steel and the like, and thereafter detonatingan explosive placed upon the cladding metal to urge the cladding metalagainst the base metal at a very high speed by the detonation pressure`of the explosion. Such process is called the explosive bonding method.

In order to maintain the space between the cladding metal and the ibasemetal in the widely-known explosive bonding method, there are two knownmethods; in one method the cladding metal is maintained at an angle offrom l to 32 relative to the base metal (which will be called the anglemethod, hereinafter) in the other method the `cladding metal and thebase metal are maintained parallel with eachother (which will be calledthe parallel method, hereinafter). According to either of the twomethods, it is possible to strongly bond a metal plate with anotherplate of the same or different kind, as compared with conventionalprocesses for preparing clad plates.

However, when the surface area of the cladding metal and the base metalare large as for example, a square of 500 mm. x 500 mm., the followingfaults have been observed even in said conventional explosive bondingmethods. In the clad plate prepared by the parallel method of explosivebonding, there often is produced a poor bonded region in a locationdistant from the initiation point and, additionally the explosive bondbetween the cladding metal and the base metal consists of a hard andbrittle inferior alloy zone. Thus the bonding strength of 3,377,693Patented Apr. 16, 196B ICC the cladding metal and the base metal is Weakand is hard to be mechanically worked. The reason why the above occursmay be explained as follows. During the explosive bonding, air betweenthe cladding metal and the base metal is pushed to the regions distantfrom the initiation point and is nally expelled. Air between thecladding metal and the base metal distant from the initiation point ismore easily expelled than air near the initiation point. Thus, furtherthe explosive bonded point is from the initiation point, the easier airbetween the cladding metal and the base metal may be expelled.Therefore, the space between the cladding metal and the base metal tendsto be reduced in spite of placing a spacer in the gap. The space becamesgradually smaller and finally becomes smaller than that necessary forthe explosive bonding. There thus occurs a poor bond in regions distantfrom the initiation part. When the cladding metal co1- lides with thebase metal, the surfaces thereof facing each other are melted to formthe so-called metal jet. It may be considered according to the essenceof the bonding mechanism of the parallel spacing method that a part 0fsaid metal jet is captured between the cladding metal and the base metaland, at the same time, another part of the metal jet is removed togetherwith air between the cladding metal and the base metal. However, whenthe space between the cladding metal and the base metal becomes smallerin such a case as described above, the cladding metal collides with thebase metal before the metal jet is removed completely. Finally, themetal jet is captured between the cladding metal and the base metal inthe form of a further thicker bonding zone (as the hard and brittleinferior alloy zone).

Therefore, there occurs a poor bond in some regions of the clad platethus obtained and further the cladding metal is connected with the basemetal in the bonding zone with a hard and brittle inferior alloy, sothat the bonding strength of the clad plate is weak and it is diicult towork the clad plate mechanically.

On the one hand, in the clad plate prepared by explosive bondingaccording to the angle method, a large internal strain in materialproperty due to work harden ing is produced and the workability and thecorrosion resistibility are inferior as compared with the inherentproperties of the cladding metal and base metal. There are sometimespresent cracks in the plate thus obtained. The reason for this may beexplained as follows.

For example, even in case the space is maintained by inclining thecladding metal at the angle of 5 relative to the base metal at thejuncture, the space .of the openside edge between the cladding metal andthe base metal is as great as 87.5 mm., in the preparation of 1000i mm.x 1000 mm. square clad plates. If the cladding metal collides with thebase metal at a high speed in the case as mentioned above, the claddingmetal is forced to undergo deformation beyond the yield point of thecladding metal itself, and the cladding metal is subjected to excessiveworkhardening whereby there are sometimes formed cracks. Further, thebase metal is subjected under cold working to a tension in thedetonating direction by collision with the cladding metal and thensubjected to excessive workhardening.

As the periphery of the clad plates is not sniliciently bonded by theconventional explosive bondingr processes,

. the periphery of the plates thus obtained should be reremoved forpractical use.

One object of the present invention is to provide a process forpreparing clad plates containing only vely small amounts of poor bondedregions, inferior alloy zones, excessive workhardened parts and cracks.Another object is to provide a process for preparing clad plates whichhave acceptable properties over the whole area thereof and whoseperiphery requires no substantial removal.

The said objects of the present invention can be achieved by placing thecladding metal on the base metal, maintaining the space between thecladding metal and the base metal relative so that the angle of thecladding metal to the base metal may be larger (in the detonatingdirection of the explosive) in the distant regions than in the regionsin the neighborhood of the initiation point, placing an explosive on abuffer above said cladding metal and detonating said explosive.

The effect .of the present invention can sufficiently be displayed onlyin case of bonding a metal of plate of a size greater than 500 mm. x 500mm., with another plate ofthe same or different kind. In case of usingmetal plates of less than said area, the present invention has noimproved effects as compared with said parallel or angle method.Suitable cladding metal according to the present invention is limited toa relatively thin and ilexible material of about 1:2 to 4 mm. inthickness. In the case of bonding the claddingmetal with the same metalin the manner as specified a'bove, the -cladding metal is maintainedabove the base so that the angle between the cladding metal and the basemetal in the space between the cladding metal and the base metal may befrom 0.1 to 0.5 in the neighborhood .of the initiation point, that is,in the range of 45 to 80% of the base metal length in the detonatingdirection of an explosive and may be from 0.3 to 1.2 in the distantregion, but larger in the distant region than in the neighborhood of theinitiation point.

The space between the claddng metal and the base metal is dependent uponthe kind and thickness of the cladding metal and in the kind and amountof the ex plosive. In general if the cladding metal is thin, it isnecessary to increase the base metal length of the initiation pointregion, that is, the angle range of 0.1 to 0.5 between the claddingmetal and the base metal and to use lower values of said angle range. Onthe one hand, it the cladding metal is thick, desirable results areobtained by decreasing the |base metal length of the initiation pointregion, that is, the angle range of 0.1 to 0.5 between the claddingmetal and the base metal and using higher values of said angle range.The reason why the base metal length of the initiation point region inthe detonating direction of an explosive is limited to a value between45 and 80 is that, if the length of the initiation point region is lessthan 45%, the open end of the angular space between the cladding metaland the base metal becomes too great and consequently the clad platethus obtained is subjected to the same excessive workhardening as theclad plate prepared by the explosive bonding of the angle method.Alternatively if said length is more than 80%, the eifect of maintainingthe cladding metal at two diierent inclinations is lost. The reason whythe angle of the cladding rnetal to the base metal in the neighborhoodof the initiation point in the space between the cladding metal to theibase metal is limited within from 0.1 to 0.5 is that, if said angle isless than 0.1", the metal jet formed between the cladding metal and thebase metal during the explosive bonding can hardly be removed with theair between the cladding metal and the base metal and, if said angle ismore than 0.5", the metal and the base metal becomes too great and theclad plate thus obtained is subjected to excessive workhardening.

The reason why the angle of the cladding metal relative to the basemetal in the regions distant from the neighborhood of the initiationpoint is limited to a valve within 0.3 and 1.2 is that, if said angle isless than 03, the metal jet formed between the cladding metal and thebase metal can hardly be removed with the air between the cladding metaland the base metal, and, if said angle is more than 1.2, the clad plateis subjected to excessive workhardening. In this case, it is necessaryto keep said l angle in the distant regions larger than that in theneighborhood of the initiation point.

Next, as the means of maintaining the space between the cladding metaland the base metal in such a manner as described above, it is possibleto freely employ any appropriate means such as placing on the base metalspacers or supporting rods of metal foils or plates 0f the same kind aseither the cladding metal or the base metal or of a different kind fromthe two, or suspending the cladding metal above the `base metal. Whenthe space can not be maintained due to a change in the kind of metal,the bonding can successfully be made by previously forming a part of thecladding metal in to the required shape.

In the practice of the present invention, it is desirable with somemetals to remove any dirt from the surfaces of the cladding metal andthe base metal which are to be bonded by physical treatments with sandpaper or a grinder, or by chemical treatments.

Suitable cladding metal and base metal in the practice of the presentinvention include mild steel, nickel, chromium, cobalt, titanium,zirconium, tantalium, aluminum, manganese, molybdenum and copper platesand alloy plates containing the above metals as the principalconstitutent. The thickness of the cladding metal is about 1.2 to 4 mm.and is less than that of the base metal. It is desirable that the areaof the cladding metal is larger than that of the base metal, forexample, larger by about 30 mm. than that of the base metal along twosides in the case where the cladding metal and the base metal arerectangular. The cladding metal is placed so that each side of thecladding metal protrudes by at least l() mm. beyond the correspondingedge 0f the base metal.

A suitable explosive according to the present invention is a powderexplosive consisting of 5 to 40% pentaerithrite tetranitrate, 3 to 13%starch, 54 to 87% low density ammonium nitrate and 1 to 3% water. A linewave generator to be used for the initation of the explosive consists ofa triangular plate constituted of plywood, plastic, steel, etc., aprimer cord to be attached to the longer side of the triangular plateand an explosive placed on the triangular plate. The shape of saidtriangular plate is determined by taking into account the detonationvelocity of the primer cord attached to the longer side of the triangleand the detonation velocity of the explosive so that the detonatingdirection at the explosive is parallel with the two side-faces of thecladding metal.

A suitable butler according to the present invention may be adhesivetape, rubber, lacquer and a plastic-containing paint, etc.

As the modication of the present invention, a notch can be formed in thecladding metal conforming to the shape of the base metal having aslightly larger area than the base metal, the cladding metal above thebase metal being placed so that said notch coincides with the peripheryof the -base metal. Thereby, the periphery of the obtained clad platecan be made in good condition.

For a further understanding of the present invention, a detailedexplanation is given below, with reference to the drawing, wherein:

FIG. l is a cross-sectional view of an arrangement for producing cladplates by the conventional parallel method;

FIG. Z is a cross-sectional view of an arangement for producing cladplates by the conventional angle method;

FIG. 3 is a cross-sectional View of an arrangement for producing cladplates according to the present invention;

FIGS. 4a and 5a are plan views showing a difference in the detonatingdirection of an explosive due to the initiation method employed by thepresent invention and illustrating the relations of points A, B and C inthe space between the cladding metal and the base metal shown in FIG. 3;

FIGS. 4b and 5b show au example of the disposition l of a spacer placedon the base metal, respectively in FIGS. 4a and 5a;

FIG. 6 is a cross-sectional view similar to FIG. 1 showing amodification thereof;

FIG. 7 is a photomicrograph (magnification of 100) of a bimetallicassembly prepared in accordance with the present invention;

FIG. 8 is a photomicrograph (magnification of 100) of a bimetallicassembly prepared in accordance with the parallel method;

FIG. 9 represents a schematic depiction of the phenomenon which isybelieved to occur in the course of the present process, and

FIG. represents a schematic depiction of the phenomenon which isbelieved to occur in the course of the parallel method of the prior art.

FIG. 1 shows a base metal 2 placed on a support 1, a cladding metal 4 isplaced on base metal 2 in spaced relation with .a gap of at least 0.0254mm. between the cladding metal and the base metal. The gap is obtainedby using a spacer 3. An explosive 6 is placed on a buffer 5 above thecladding metal 4, and a line wave generator '7 and detonator 8 aremounted in contact with the explosive. The explosive 6 is detonated toproduce the clad plate.

In FIG. 2 the cladding metal 4 is maintained on the base metal 2 at anangle of 1 to 32 by the spacer 3, and then, in the same manner as inFIG. 1, explosive bonding is effected to produce the clad plate.

`In FIG. 3 is shown the process of the present invention, wherein thebase metal 2 is placed on the support 1 and the cladding metal 4 ismaintained on the base metal 2 by the spacer 3 so that the angle of thecladding metal 4 to the base metal 2 is larger in the region mostdistant from the initiation point of the explosion (region B-C) ascompared to the angle in the neighborhood of the initiation point(region A-B).

In this case, the extent of the A-B region is 45 to 80% of the basemetal length in the detonating direction of the explosive 6, the angleof the cladding metal 4 to the base metal 2 being 0.1 to 0.5 The extentof the B-C region, is to 55% of the ybase metal length, and the angle ofthe cladding metal 4 to the base metal 2 is 0.3 to 1.2?. As describedabove, the angle of the cladding metal 4 to the base metal 2 is largerin the region B-C than in the neighborhood of the initiation point. Itis also desirable that the space between the cladding metal and the basemetal be 0.8 to 2.0 mm. at point A. Then, the buffer 5 is placed on thecladding metal 5, a frame is provided along the periphery of thecladding metal, the powder explosive 6 is placed, the line wavegenerator 7 and the electric detonator 8 are mounted and the powderexplosive 6 is detonated to produce the clad plate.

Further, in case of detonating the explosive 6 the detonating directionvaries with the initiation method employed, so further explanation isgiven in FIGS. 4 and 5 to make clear at what places on the base metal 2there are disposed points A, B and C shown in FIG. 3. FIG. 4a representsthe case in which a triangular line wave generator 7 consisting of thesame explosive as the powder explosive 6 is utilized and the primer cord7 which is attached to the longer side of the line wave generator (andhas about 3 times the detonation velocity of the powder explosive) isinitiated by the electric detonator 8. In this case, the detonatingdirection of the explosive is indicated by the arrows, so points A`, Band C on the base metal shown in FIG. 3 correspond to lines A, B and Cin FIG. 4. FIG. 4b shows the disposition of the spacers placed on thebase metal in FIG. 4a. FIG. 5a illustrates a case in which the electricdetonator 8 is mounted in the center of a side of the powder explosive6, and the detonating direction of the explosive is radial as shown ybythe arrow heads.

6 FIG. 5b shows the disposition of the spacers on the base metal in FIG.5.

FIG. 6 shows an arrangement wherein a notch 10 is previously provided onthe cladding metal 4 having a slightly larger area than the base metal,the disposition of the notch being fitted to the periphery of the basemetal 2, the space between the cladding metal and the base metal beingobtained by maintaining the cladding metal with the spacer 3 so that theangle of the cladding metal 4 with the base metal 2 is larger in theregion distant from the neighborhood of the initiation point in thedetohating direction. The explosive 6 is placed on the buffer 5 abovethe cladding metal as in the arrangement of FIG. 3, and the line wavegenerator 7 and the electric detonator 8 are mounted after which theexplosive 6 is detonated to produce the clad plate. In the practice ofthe process according to the present invention as shown in FIG. 3, thesurplus edge of the cladding metal is sheared by the periphery of thebase metal when the cladding metal coliides with the base metal at avery high velocity during the explosive bonding, so a part of thedetonation pressure required for the explosive boliding is spent andconsequently there sometimes occur regions of poor bonding in theperiphery of the clad plate. This phenomenon tends to be more pronouncedwith increased thickness of the cladding metal. If the notch 10 isprovided in the cladding metal as shown in FIG. 6 when the claddingmetal is of 2 to 4 mm. in thickness, the periphery of the clad plate isfree of regions of poor bonding. The depth of the notch varies with thethickness of the cladding metal, but is less than 70%, and is preferably30%, of the thickness of the cladding metal. It is desirable that thenotch in the cladding metal be formed in the upper surface thereof asshown in FIG. 6, but the effect is not significantly different fromnotching the surface facing the base metal.

In the photomicrograph of FIG. 7, A indicates a base layer -of carbonsteel, B indicates a cladding layer of titanium and C indicates theinterface waves. In the photomicrograph of FIG. 8, A indicates a baselayer of carbon steel, B indicates a cladding layer of titanium and Dindicates the bonding zone composed of material from layers A and B.

In FIG. 9, 2 represents the base metal layer, 4 represents the claddingmetal layer, 6 represents the layer of explosive before detonation, and6 represents the gaseous detonation products following detonation oflayer 6, 14 represents a sharp liquid stream of material composed ofboth layers 2 and 4 which impinges on the underside of layer 2 justahead of the impact point 13.

In FIG. 10, 16 represents the material immobilized between the layers 2and 4 and bonding these layers together, 14 represents the jettedmaterial which is recirculated to give intimate mixing of the twometals.

The present invention is further illustrated by the following examplesgiven for the purpose of illustration only, but not limiting theinvention, and wherein the percentages are by weight.

Exam-ple 1 An explosive is used which is a powder explosive consistingof 10% pentaerithrite tetranitrate, 12% starch, 76% low density ammoniumnitrate and 2% water content, and having a detonation velocity of 1900m./se. The cladding metal is a titanium plate (2 mm. x 1000 mm. x 2000mm.) and the base metal is a mild steel plate (16 mm. x 970 mm. x 1970mm.). A masking tape was applied to the cladding metal surface facingthe explosive. First, after the upper surface of the base metal waspolished with a grinder, the base metal was placed on a sand supportand, as shown in FIG. 4b, V-shaped spacers of 0.15 mm. in height made of1.0 mm. thick nickel foil were placed at intervals of 200 mm. on line Aon the base metal, and similarly, there were placed spacers of 1.5 mm.in height on line A', of 2.0 mm. in height on line A", of 2.5 mm. inheight on line B and of 4.3 mm. in height on line C, respectively. Theintervals between lines A, A', A and B were 230 mm. respectively and theinterval lines B and C was 300 mm. On the spacers thus disposed, saidcladding metal was placed. In this case, the distance between lines Aand B was equal to 70% of the base metal length in the detonatingdirection of the explosive, where the angle of the cladding metal to thebase metal was 0.18, while the distance between lines B and C was equalto 30% of the base metal length, where the angle of the cladding metalto the base metal was 0.35". Then, as shown in FIG. 4, a triangularplate made of mm. thick plywood was attached to the longer side of thecladding metal near line A. A primer cord was fixed with the tape alongthe longer side of this triangle. Within a card board frame attached tothe cladding -metal and the outside of plywood, said explosive wasuniformly disposed, in the ratio of 7 kg. per square meter, on themasking tape. A No. 6 electric detonator was attached to an end of theprimer cord, and thereby the primer cord and the explosive weredetonated. By exploding the explosive, mild steel and titanium werefound to be firmly and uniformly bonded together to form a compositeassembly. The same materials and explosive as in the preparation of cladplates according to the procedure of the present invention were used bythe angle method (angle 5) and the parallel method (space 1.0 mm.)respectively to produce clad plates. Various test pieces were removedfrom a region distant from the intiation point in the obtained cladplates respectively and the results of various tests are compared inTable l.

As clearly shown in Table 1, the result of ultrasonic examination on thebonding strength of the clad plates obtained according to the process ofthe present invention verifies that there are no poor bonded parts. Theshear strength of this clad plate was measured according to the ASTM(A263-63), and found to be 35 kg. per square millimeter, more than twotimes the provided value according to the ASTM. Similarly, no failurewas observed in the bend test according to the ASTM. The result of thetension test was also excellent. Further, a strip-like inferior alloyzone was not observed in the bonding surface under a microscope.

In contrast to this, though the clad plates obtained by the parallelmethod had no apparent defects, there were observed a number of poorbonded regions from the test result on the bonding strength due to theultrasonic examination. Further, the shear strength thereof measuredaccording to the ASTM was lower than that of the clad plate prepared inaccordance with the present invention. In the face bend test, the cladplate was broken away at the bonding surface. By observing the bondingsurface part under a microscope, the presence of a 35a wide striplike,hard and brittle inferior alloy zone was verified.

In the clad plate obtained according to the angle method, many crackswere observed in the surface of the cladding metal, and a surfaceprojection appeared in the regions Where the bonding surface containedlarge spacers. Further, under the face bend test, many cracks which wereassumed to be caused by severe workhardening occurred in the bondingsurface region. It was also verified by the tension test that elongationwas decreased significantly.

As is clear from the comparison of said test results, the poor bondedpart which was observed in the clad plate prepared by the parallelmethod was not observed in the clad plate in accordance with the presentinvention. The clad plate in accordance with the present invention wasexcellent in the face bend test.

In the clad plate prepared according to the parallel method, thecladding metal is connected with the base metal through a strip-likealloy zone. In the clad plate prepared according to the presentinvention, the cladding metal is directly connected with the base metalwithout the alloy zone. This may indicate a difference in the bondingmechanism between the parallel method and the process of the presentinvention.

In other Words, as a suitable angle determined by the detailed testresults is provided between the cladding metal and the base metal, thejetted material is removed in the detonating direction to the open endin the space between the cladding metal and the base metal, withoutbeing recirculated (sce FIG. 9).

The surfaces of the cladding metal and the base metal facing to eachother are changed to a fresh surface by the occurrence of the metal jetand are pressed by each other duc to the high pressure of the explosion,so it may be thought that the metallurgical bonding of the claddingmetal with the base metal can be carried out without the bonding zone.

On the other hand, in the parallel method, a jet composed of surfacelayers of both metals may be produced, this jet being directed into theas yet unoccupied space betweeen the layer of cladding metal and thesurface of the metal being clad. This jetted material is recirculated togive intimate mixing of the two metals (see FIG. l0).

As described above, the mechanism in the parallel method is understoodby assuming that the cladding metal is connected through the bondingzone with the base metal.

It was also verified that the clad plate prepared according to thepresent invention had no apparent defects as compared with the cladplate according to the angle method and was an excellent clad plate oflittle workhardening.

Excimple 2 The cladding metal used here is a titanium plate (2.5 mm. x1000 mm. x 2000 mm.) and the base metal is a stainless steel plate (14mm. x 970 mm. x 1970 mm.).

After polishing the upper surface of the base metal with a grinder, thebase metal was placed on a sand support. As shown in FIG. 5b, on lineA-C, V-shaped spacers of 1.0 mm., 1.7 mm., 2.4 mm. and 3.1 mm. in heightrespectively made of 0.15 mm. thick nickel foil were placed from theinitiation point at intervals of 200 mm., and a 5.9 mm. high spacer isplaced at point C'. Similarly, spacers of 2.6 mm. and 3.4 mm. in heightwere respectively placed at 'points of 40% and 60% of the base metallength from the initiation point on line A-C", and a 6.5 mm. high spacerwas placed at point C. Moreover, spacers of 2.0 mm., 3.0 mm. and 4.0 mm.in height were respectively placed at points of 20%, 40% and 60% of thebase metal length from the initiation point on line A-C", and a 8.0 mm.high spacer was placed at point C". Moreover, at the center of C-C-C",250 mm. from the initiation point, spacers of 6.2 mm. and 7.2 mm. wererespectively placed. On the spacers thus disposed, said cladding metalwas placed. In this case, the distance between `point A and line B wasequal to 60% of the base metal length in the dctonating direction of theexplosive, where the angle of the clad-ding metal to the base metal was020, while the distance between lines B and C was equal to 40% of thebase metal length, where the angle of the cladding metal to the basemetal was 0.40". Within a cardboard frame attached to the outside of thecladding metal thus disposed, the same explosive as in Example l wasplaced uniformly in the ratio of 8 kg. per square meter. As shown inFIGS. 5a and 5b, an electric detonator was attached to point A Where thespace between the cladding metal and the base metal was the smallest,and thereby the explosive was detonated.

Under the explosion of the explosive, the stainless steel and titaniumplates were found to be firmly and uniformly bonded together to form acomposite, assembly. From the test results on the bonding strength ofthe obtained clad plate according to the ultrasonic examination, therewas observed no poor bonded regions. The shear strength thereof Was morethan 2 times the provided Value in accordance with the ASTM. Further,the results of the bend test and the tension test were alsosatisfactory. No striplike inferior alloy zone was present in thebonding surface region, under microscopic observation.

TABLE 1 [The present invention] Sh T t Bend Test Tension Test ear esShear Strength Reverse Tensile Elongaton (kg/mm!) Face Bend BendStrength (Percent) (kg./rnm.2)

36. 2 41. 2 4". 5 32. 3 40.9 sail Good Gooo {4i-r 32.1

[Parallel method] Sh T t Bend Test Tension Test ear es Shear Strength lReverse Tensile Elongation (kg/mm 2) Face Bend Bend (trngthZ) (Percent)-g. mm.

30. 7 14. 3 4 12.1 20. i Sopofotoo Good [Angle method] Sh T t Bend TestTension Test ear es Shear Strength Reverse Tensile Elongation (kg/mm!)Face Bend Bend (tr/engtl) (Percent) g. mm.

30.1 21. 0 49. 8 2G. 5 23.5 14.1 icrook Good {49.2 24.8

Example 3 The cladding metal used here is a titanium plate (4.0 mm. x1000 mm. x 1500 mm.) and the base metal is a mild steel plate mm. x 970mm. x 1470i mm). In the cladding metal, there was previously provided anotch of about 1 mm. in depth having a V-shaped cross-section, the notchcorresponding to the peripheral shape of the base metal. After polishingthe upper surface of the base met-a1 with a grinder, the base metal wasplaced on the sand support. On said upper surface, as shown in FIGS. 4aand 4b, line B was provided at a distance of 50% of the base metallength in the detonating direction, that is, 485 mm. V-shaped spacers of0.8 mm. in height made of 0.15 mm. thick nickel foil were placed on lineA. Further, said spacers of different height in turns were placed atcertain intervals so that the angle of the cladding metal to the basemetal is 0.35 in the region between lines A and B and 0.6 in the regionbetween lines B and C. Then, as shown in FIG. 6, the cladding metal wasplaced on said spacers by coincidence of the notch with the periphery ofthe base metal. The same line wave generator as in Example 1 wasattached, and the powder explosive of the same blending as in Example lwas uniformly placed in the ratio of 9.5 kg. per square meter on themasking tape covering the cladding metal and was detonated yby anelectric detonator attached to an end of a` primer cord, to obtain aclad plate consisting of titanium and mild steel. y

The results of the shear test, bend test and tension test on theobtained clad plate were the same as in Example 1. It was further veriedby the ultrasonic examination that the bonding was perfect not only inthe middle of the clad plate but also in the periphery where the bondingwas difficult in case the thickness of the cladding metal was large.Even under the microscopic observation, there was present no inferioralloy zone.

Example 4 The cladding metal used here is an arms bronze plate (3 mm. x1000 mm. x 1000 mm.) and the base metal is a mild steel plate (16 mm. x970 mm. x 970 mnt). In the cladding metal, there was previously provideda notch of about 1 mm. in depth having V-shaped cross-section, notchcorresponding to the peripheral shape of the base metal. After polishingthe upper surface of the base metal with a grinder, the base metal wasplaced on the sand support. On said upper surface, as shown in FIGS. 4aand 4b, line B was provided at a distance of 55% of the base metallength in the detonating direction. V-

lil

shaped spacers of 1.0 mm. in height made ol 0.15 mm. thick nickel foilwere placed on line A. Further, spacers of different height in turnswere placed at certain intervals so that the angle of the cladding metalto the base metal is 025 in the region between lines A and B, while itis 0.5 in the region between lines B and C. Supporting rods are placedat a point beyond line C. Then, as shown in FlG. 6, the cladding metalwas placed on said spacers and supporting rods by coinciding the notchwith the periphery of the base metal.

The same line wave generator as in Example 1 was attached, and thepowder explosive of the same blending as in Example 1 was uniformlyplaced in the ratio of l2 kg. per square meter on the masking tapecovering the cladding metal and was detonated by an electric detonatorattached to an end of a primer cord, to obtain a clad plate consistingof armsbronze and mild steel. It was veried by the same tests as inExample 1 that the Whole surface of the obtained clad plate wassufciently bonded and the mechanical properties of the clad plate wereexcellent.

Example 5 The explosive used here is a powder explosive consisting of10% pentaerithrite tetranitrate, 3% starch, 85% low density ammoniumnitrate and 2% water. The cladding metal is a tantalium plate (1.2 mm. x500 mm. x 750 mm.) and the base metal is a mild stel plate (l0 mm. x 480mm. x 730 mm). After polishing the upper surface of the base metal witha grinder, the base metal was placed on the sand support. As shown inFlGS. 5a and 5b, line B was provided at a distance of 70% of the basemetal length in the detonating direction. V-Shaped spacers of 0.8 mm. inheight made of 0.15 mm. thick nickel foil were placed on line A, so thatthe angle of the cladding metal to the base metal is 0.1 in the regionbetween point A and line B and 0.3 in the region between lines B and C.For maintaining said angle of the cladding metal to the base metal,V-shaped spacers made of 0.15 mm. thick `were placed on the periphery ofthe base metal and, as for the residual part, a nylon yarn was attachedwith plastic adhesive to the upper surface and the required angle couldbe obtained by suspending the nylon yarn. Thus, the required angle ofthe cladding metal to the base metal could be maintained by using saidspacers and nylon. Said explosive was uniformly placed in the ratio of 7kg. per square meter on a plastic paint covering the cladding metal. Anelectric detonator was attached to the point A where the space betweenthe cladding metal and the base metal was the smallest and the explosivewas detonated to obtain a clad plate consisting of tantalium and mildsteel. It was verified by the same tests as in Example l thaL the wholesurface of the obtained clad plate was sufficiently bonded and themechanical properties of the clad plate were excellent.

Example 6 The cladding metal used here is a Monel plate (4.0 mm. x 1000mm. x 1000 mm.) and the base metal is a mild steel plate (40 mm. x 970mm. x 970 mm.). ln the cladding metal, there was previously provided anotch of about 2 mm. in depth having a V-shaped cross-section the notchcorresponding to the peripheral outline of the base metal. Afterpolishing the upper surface of the base metal with a grinder, the basemetal was placed on the sand support. On said upper surface, as shown inFGS. 4 and 4', line B was provided at a distance of 50% of thc basemetal length in the detonating direction. V-shaped spacers of 1.0 mm. inheight made of 0.2 mm. thick nickel foil were placed on line A. Spacersof different height in turn were placed at certain intervals so that theangle of the cladding; metal to the base metal is 0.4 and 0.6" in theregion between lines A and B and between lines B and C, respectively.The cladding metal which was previously formed to have said angle ofabout 0.2 at the position distant from the base metal edge by 50% of thecladding metal length was placed on said spacers so that the notch ofthe cladding metal was in concidence with the periphery of the basemetal. The same line wave generator as in Example l was attached and thepowder explosive of the same blending as in Example 1 was uniformlyplaced in the ratio of 18 kg. per square meter on the masking tapecovering the cladding metal and was detonated by an electric detonatorattached to an end of a primer cord, to obtain a clad plate consistingof Monel and mild steel. It was verified that the whole surface of theobtained clad plate was sutiiciently bonded and the mechanicalproperties of the clad plate were excellent.

Example 7 The cladding metal used here is a zirconium plate (2 mm. X 500min. x 1000 mm.) and the base metal is a mild steel plate (16 mm. x 480mm. x 980 mm.). After polishing the -base metal surface with a grinder,the base metal was placed on the sand support. As shown in FIGS. 5a and5b, line B was provided at a distance of 65% of the base metal length inthe detonating direction. At the point A, a V-shaped spacer of 0.8 mm.in height made of 0.15 mm. thick nickel foil was placed so that theangle of the cladding metal to the base metal is 0.2 in the regionbetween point A and line B, while said angle was maintained at 0.35 inthe region between lines B and C by placing spacers of different heightin turn at certain intervals. The cladding metal was placed on saidspacers, the explosive of the same blending as in Example 5 was wasuniformly placed in the ratio of 8 kg. per square meter on masking tapecovering the cladding metal, and further a 30 mm. thick sand layer wasplaced on thin paper covering this explosive so as to use the detonationpressure of the explosive effectively. As shown in FIG. 5a, an electricdetonator was attached to point A where the space between the claddingmetal and the base metal was the smallest, and thereby the explosive wasdetonated, to obtain a clad plate consisting of zirconium and mildsteel. It was verified that the whole surface of the obtained clad platewas sufciently bonded and the mechanical properties of the clad platewere excellent.

Example 8 The cladding metal used here is a nickel plate (2 mm. x 1000mm. x 1000 mm.) and the base metal is a mild steel plate (20 mm. X 970mm. x 970 mm.). After polishing the base metal surface with a grinder,the base metal was placed on the sand support. As shown in FIGS. 4a and4b, line B Was provided at a distance of 70% of the base metal length inthe detonating direction. V-shaped spacers of 1.0 mm. in height made of0.15 mm. thick nickel foil were placed on line A. Spacers of differentheight in turn were placed at certain intervals so that the angle of thecladding metal to the base metal is 0. in the region between lines A andB and 0.3 inthe region between lines B and C.

On the spacers, the cladding metal was placed and the same line wavegenerator as in Example 1 was attached. The powder explosive of thesa-rne blending as in Example 5 was uniformly placed in the ratio of 10kg. per square meter on masking tape covering the cladding metal, andwas detonated by an electric detonator attached to an end of a primercord, to obtain a clad plate consisting of nickel and mild steel.

The obtained clad plate was of good quality.

Example 9 The cladding metal used here is an aluminum plate (2 mm. x1000 mm. x 1000 mm.) and the base metal is a mild steel plate (12 mm. x980 mm. x 980 mm.).

The explosive of the same blending as in Example 5 was used in the ratioof 6 kg. per square meter. By the same procedure as in Example 8, agood-quality clad plate consisting of aluminum( and mild steel wasobtained.

Example 10 The cladding metal used here is a Hastelloy-C plate (1.5 mm.x 1000 mm. x 1000 mm.) and the base metal is a mild steel plate (22 mm.X980 rnrn. x 980 mm.).

The explosive of the same blending as in Example 5 was used in the ratioof 10 kg. per square meter. By the same procedure as in Example 8, agood-quality clad plate consisting of Hastelloy-C and mild steel wasobtained.

Example I1 The cladding metal used here is a tantalium plate (1.5 mm. x500 mm. x 1000 mm.) and the base metal is a stainless steel plate (12mm. x 480 mm. x 980 mm.).

After polishing the base metal surface with a grinder, the base metalwas placed on the sand support. As shown in FIGS. 4a and 4b, line B wasprovided at a distance from the base metal edge of 70% of the base metallength in the detonating direction. V-shaped spacers of 0.8 mm. inheight made of 0.15 mm. thick nickel foil were placed on line A.Further, spacers of different height in turn were placed at certainintervals so that the angle of the cladding metal to the base metal is0.1 in the region between lines A and B and 0.3 in the region betweenlines B and C.

On these spacers the cladding metal was placed, and the same line wavegenerator as in Example l was mounted. The explosive of the sameblending as in Example 5 was uniformly placed in the ratio of 8 kg. persquare meter on masking tape covering the cladding ymetal and wasdetonated by an electric detonator attached to an end of a primer cord,to obtain a clad plate consisting of tantalium and mild steel. Theobtained clad plate was of good quality.

Example 12 The cladding metal used here is a stainless steel plate (2mm. x 1000 mm. x 1000 mm.) and the base metal is a mild steel plate (16mm. x 970 mrn. x 970 mm.).

The explosive of the same blending as in Example 1 was used in the ratioof 7 kg. per square meter. By the same procedure as in Example 8, agood-quality clad plate consisting of stainless steel and mild steel wasobtained.

Example 13 The cladding metal used here is a copper plate (2 mm. X 1000mm. X 1000 mm.) and the base metal is a mild steel plate (16 mm. x 980mm. x 980 mm.).

As shown in FIGS. 5a and 5b, line B was provided at a distance of 70% ofthe base metal length in the detonating direction. V-shaped spacers of1.0 mm. in height made of 0.15 mm. thick nickel foil were placed on lineA. Spacers of different height in turn were placed so that the angle ofcladding metal to the base metal is 0.2 in the region between line A andline B and 0.35 in the region between lines B and C.

The cladding metal was placed on said spacers, the explosive of the sameblending as in Example 5 was uniformly placed in the ratio of 8.5 kg.per square meter on masking tape covering the cladding metal, and anelectric detonator was attached as shown in FIGS. 5a and 5b to point Awhere the space between the cladding metal and the base metal was thesmallest and thereby the explosive was detonated, to obtain a clad plateconsisting of copper and mild steel. The obtained clad plate was a goodquality.

Example I 4 The cladding metal used here is an Inconel plate (2 mm. x1000 mm. x 1000 mm.) and the base metal is a mild steel plate (20 mm. x970 mm. x 970 mm.). The explosive of the same blending as in Example lwas used in the ratio of 8 kg. per square meter. By the same pro-Example 15 The cladding metal used here is a cupronickel `plate (2 mm. x1000 mm. x 1000 mm.) and the base metal is a mild steel plate (30 mm. x970 mm. x 970 mm.).

Theexplosive of the same blending as in Example l was used in the ratioof 8 kg. perfsquare meter and by the same procedure as in Example 8 agood-qual-ity clad plate consisting of cupronickel and mild steel wasobtained.

Example 16 'Ihe cladding metal used here is an armsbronze plate (4 mm. x730 mm. x 730 mm.) and the base metal is a mild steel plate (45 mm. x700 mm. x 700 mm.). In the cladding metal, there was previously provideda notch of about 1 mm. in depth having a V-shaped cross-section, andcorresponding to the peripheral outline of the base metal.

After polishing the upper surface of the base metal with a grinder, thebase metal was placed on the sand support. On this upper surface, asshown in FIGS. 4a and 4b, line B was provided at a distance' of 50% ofthe base metal length in the dentonating direction. V-shaped spacers of1.5 mm. in height made of 0.2 mm. thick nickel foil were placed on lineA. Spacers of dilerent height in turn were placed at certain intervalsso that the angle of the cladding metal to the base metal was 0.5 in theregion between lines A and B and 1.2 in the region between lines B andC, with control of the spacers placed on line C at the edge of the basemetal.

The cladding metal was placed on said spacers, the notch coinciding withthe periphery of the 'base metal. The same line wave generator as inExample 1 was mounted, and the powder explosive of the same blending asin Example 1 was uniformly placed in the ratio of 15 kg. per squaremeter on masking tape covering the cladding metal and further a 30 mm.thick sand layer was placed on thin paper covering the explosive. Bydetonating the explosive With an electric detonator attached to an endof a primer cord, a good-quality clad plate consisting of armsbronze andmild steel was obtained.

Example 17 The cladding metal used here is a stainless steel plate (4mm. x 930 mm. x 930 mm.) and 4the base metal is a mild steel plate (50mm. x 900 mm. x 900 mm.). In the cladding metal, there Was previouslyprovided a notch of about 2 mm. in depth having a V-shapedcross-section, and corresponding to the peripheral outline of the basemetal.

After polishing the upper surface of the base metal with a grinder, theVbase metal was placed on the sand support. On this upper surface, asshown in FIGS. 4a and 4b, line B was provided at a distance of 45 of thebase metal length in the detonating direction. V-shaped spacers of 1.0mm. in height made of 0.2 mm. thick nickel foil were placed on line A.Spacers of dilerent height in turn were placed at certain intervals sothat the angle of the cladding metal to the base metal was 0.4 in theregion between -li-nes A and B while said angle in the region between Band C was kept at 1.0 by placing spacers on line C at the edge of thebase metal.

'Ihe cladding met-al which had previously been formed to maintain anangle of about 0.4 at the 45% position of the cladding metal length wasplaced on said spacers, the notch coinciding with the periphery of thebase metal.

The same line wave generator as in Example 1 was mounted, and the powderexplosive of the same blending as in Example 1 was uniformly placed inthe ratio of 12 kg. per square meter on masking tape covering thecladding metal and was detonated 4by an electric detonator attached toan end of a primer cord, to obtain a goodquality clad plate consistingof stainless steel and mild steel.

Example 18 The clading metal used here is a titanium plate (4 mm. x 1000mm. x 1000 mm.) and the lbase metal is a stainless steel plate (40 umn.x 970 mm. X 970 mm). In the cladding metal, there was previouslyprovided a notch of about 1 mm. in depth having a V-sliapedcrossdsection, and corresponding to the peripheral outline of the basemetal. After polishing the upper sutiface of the base metal with agrinder, the base metal was placed on the sandpsupport. On this uppersurface, as shown in FIGS. 4a and 4b, line B was provided at a distanceof 50% of the base metal length in the 'detonating direction. V- shapedspacers of 1.5 mm. in height made of 0.2 mm. thick nickle foil wereplaced on line A, so that the angle of the clading metal to the lbasemetal was 0.415 and spacers were placed on line C to maintain an angleof 1.0 between lines B and C. The cladding metal was placed on saidspacers, with the notch coinciding with 'the periphery of Ithe rbasemetal.

The same line wave generator as in Example 1 was mounted, and the powderexplosive of the same blending as in Example 1 was uniformly placed inthe ratio of 9.5 kg. per square meter on a 1 nnn. thick mber sheetadhering closely to the cladding metal and further a 30 mm. thick sandlayer was pla'ced on thin paper covering the explosive. By detonatingthe explosive with an electric detonator attached to an end of a primercord, a good-quality clad plate consisting of titanium and stainlesssteel was obtained.

Example 19 The cladding `metal used here is a Monel plate (4 mm. X 1000x 1000 mm.) and the 'base metal a stainless steel plate (20 mm. x 970mm. x 970 mm).

The explosive of the same blending as in Example 1 was uniformly placedin the ratio o'f 15 kg. per square meter, and further a 30 mm. thicksand layer was placed on a thin sheet covering the explosive. By thesame procedure as in Example 6, a good-quality clad plate consisting olfMonel and stainless steel was obtained.

Example 20 The cladding metal used here is an armsbronze plate (2 min. x`1000 x 2000 mm.) and the -base metal is a stainless steel plate (12mlm. x 970 mm. x 1970 mm.).

The explosive of the same blending as in Example l was n'sed in theratio of 9 kg. per square meter and, by the same procedure as in Example1, a good-quality clad plate consisting of armsbronze and stainlesssteel was obtained.

Example 21 The cladding metal used here is a zirconium plate (1.5 mm. x500 x 1000 mm.) and the base metal is a stainless steel plate (112 mm. x480 mm. x 980 mm,.).

The explosive of the same blending as in Example 5 was used in the ratioof 8 kg. per square meter and, by the same procedure as in Example 11, agood-quality clad plate consisting of zirconium and stainless steel wasobtained.

Example 22 The cladding metal used here is a Hastel-loy-C plate (1.5 mm.x 1000 mm. x 1000 mm.) and the base metal is a stainless steel plate (20mm. x 980 mm. x 980 mm). The explosive of the same blending as inExample 5 was uniformly placed in the ratio of 8 k'g. per square meterand a 30 mm. thick sand layer was placed on thin paper covering theexplosive. By the same procedure as in Example 8, a good-quality cladplate consisting of Hastelloy-C and stainless steel was obtained.

l5 Example 23 The cladding metal used here is an aluminum plate (3 mm. x1000 mm. x 2000 mm.) and the base metal is a stainless steel (12 mm. x980 mm. x `1980 mm.).

As shown in FIGS. 5a and 5b, line B was provided at a distance of 70% ofthe base metal length in the detonating direction. V-shaped spacers of0.8 mm. in height made of 0.15 mm. nickle foil were placed on line A.Spacers of different height in turn were placed at certain intervals sothat the angle of the cladding metal to the base metal was 022 in theregion between point A and line B and 0.3" in the region between lines Band C. On said spacers, lthe cladding metal was placed, and theexplosive of the same 'blending as in Example 5 was uniformly placed inthe ratio of 7 kg. per square meter on a masking tape covering thecladding metal. An elec tric detonator was attached as shown in FIG. 5ato point A Where the space 'between the cladding metal and the ibasemetal was the smallest and thereby the explosive was detonated, toobtain a good-quality clad plate consisting of aluminum and stainlesssteel.

It may be understood that it is possible according to the presentinvention to eiect explosive bond-ing of mild steel, nickle, chromium,cobalt, titanium, zirconium, tantalium, aluminum, manganese, molybdenum,and copper plates and alloy plates containing said metal as theprincipal constituent with each other.

What is claimed is:

1. A process for producing a clad plate wherein a cladding plate ismounted in superposed spaced relation above a ba'se plate, and theplates are bonded together under the force of the detonation of anexplosive placed on the cladding plate, an improvement for bonding acladding plate h'aving a thickness of between 1.2 mm. and 4 mm. on abase plate of a size of at least 500 mm. x 500 mm., said improvementcomprising supporting the cladding plate in spaced relation above thebase plate such that an angle is formed in a first region between thecladding plate and the base plate of between 0.1 and 0.5" over between45 and 80% of the length of the base plate, and a larger angle is-formed in a contiguous second region orf lbetween 0.3 and l.2 betweenvthe remainder of the cladding plate and base plate, and initiating thedetonation of the explosive from one end of the first region so thatdetonation of `the explosive proceeds from the rst region to the secondregion.

2. A process as claimed in claim 1 wherein said cladding plate has aminimum spacing with the base plate at the location where the explosiveis detonated which is between 0.8 and 2.0 mm.

3. A process as claimed in claim 1 comprising interposing a buffermaterial between the explosive and the cladding plate.

4. A process as claimed in claim 1 wherein the cladding plate is ofgreater size than the base plate, the im- -provement further comprisingforming a notch in the cladding plate corresponding to the peripheraloutline of the base plate, the cladding plate being superimposed abovethe base plate with the notch in coincidence with the periphery of thebase plate.

S. A process as claimed in claim 1 wherein the cladding plate issupported in spaced relation above the base plate -by placing spacers ofspecific height on the base plate and then placing the cladding plate onthe spacers.

6. A process as claimed in claim 1 wherein the cladding plate issupported in spaced relation above the base plate by placing spacers ofspecific height on the base plate in -said lfirst region and suspendingthe cladding plate over the base plate in the second region with thecladding plate resting on the spacers.

References Cited UNITED STATES PATENTS 3,197,855 8/1965 Carter et al.29--493 X 3,258,841 7/1966 Popoli 29-497.5 X 3,263,324 8/1966 Popott'29497.5 X

CHARLIE T. MOON, Primary Examiner.

P. M. COHEN, Assistant Examiner.

